Can early treatment change root shape of a dilacerate incisor? Part 1

Published: November 2017

Bulletin #71
November 2017

Can early treatment change root shape
of a dilacerate incisor?

A 7-year old patient arrives in your office together accompanied
by his mother and a panoramic radiograph. The parent tells you that one of his
maxillary central incisors erupted about a half year ago and the other has not.

He has been referred by a pediatric dentist who has treated
the child over the past couple of years and has recognized an abnormal
orientation of the unerupted incisor. In an effort to encourage the spontaneous
eruption of this incisor, he recently extracted the other deciduous incisors in
the maxilla with the intention of providing additional space. Months later,
nothing has changed and mother is now quite concerned and sitting in your
office looking to you for answers. She rapidly draws your attention to the
panoramic film, pointing to the incisor which you recognize as dilacerate. With
careful questioning, you may find that at around the age of 2 years, the child
fell on his face, lacerated his lip and jarred his deciduous incisor. Alternatively,
however, there may be no history of traumatic injury of which the parent is
aware or, quite frequently, can remember.

Fig. 1a.Intra-oral
photographs of the initial condition at presentation with the teeth in
occlusion - age 7.5 years.

Fig. 1b. Occlusal views of the dentition- age 7.5 years.

Your intra-oral examination reveals four erupted permanent first
molars and all the primary molars and canines in both jaws. In addition to the
lone maxillary central incisor, the mandibular four permanent incisors are erupted
with a minor degree of malalignment for this early stage of the child’s dental
development (Fig. 1a, b).

Fig. 2a. Lateral view of the dentition, extracted from
the lateral cephalometric film. The dilacerate incisor is indicated (arrow).

Fig. 2b. Panoramic film of the dentition showing the
dilacerate incisor (arrow). The dental age is coincident with the chronologic
age.

From the radiographic records (Fig. 2a, b), you are
able to deduce that the child’s dental age corresponds with his chronologic age
and, as expected, each of the erupted permanent teeth has an open root apex.
The premolars and permanent canines have barely began root calcification, while
early root formation can be seen on the maxillary lateral incisors. The single
erupted maxillary incisor exhibits about half of its expected final root
length. The presentation of the dilacerate incisor on the panoramic film is through
the long axis of its crown, which would be equivalent to an occlusal view of
most other teeth. This view offers no information of the shape and length of
the root of the tooth, nor whether or not there is a root, because planar 2D
film radiography can offer very little information in the bucco-lingual plane. In
order to confirm the presence, length and form of its root, a CBCT scan needs
to be conducted.

Notwithstanding, the clear indication is that the tooth is
dilacerated in its most common and characteristic form, which I have termed the
“classic” dilaceration and which I have described in earlier postings on this
website. In the printed literature and contrary to the accepted views at the
time, I first posited a hypothesis which describes how I believe this very
special, always identical, yet unique type of anomaly occurs as a dynamic
response to a specific traumatic episode.1, 2

Question:
Is it necessary to provide a phase I treatment aimed only at the dilacerate
tooth or is it preferable to wait till the eruption of the permanent dentition
at age 12 years, when the tooth will be treated within a one-phase, comprehensive,
orthodontic treatment program?

There are three aspects to consider in relation to this
question:

1. Will the situation worsen
due to further root growth, if left untreated?

F Fig. 3a. This series of cross-sectional cuts taken from
the CBCT shows the curved root of the incisor. Note the curvature of the
developing root with a wide-open apex, which appears to be exiting the palatal border
of the alveolar ridge.

Fig. 3b. A 3D screen shot of the anterior dentition,
taken from the CBCT.

The root of a healthy maxillary central incisor continues to
elongate for about 3 years after it first appears in the mouth, until its
completion at apexification (Fig. 3a, b). Normally, the direction of the growth
of the root of a single rooted tooth is continuous with the orientation of the
crown and with the eruption path and is a contributing factor to the eruption mechanism
itself. While the root of a dilacerate tooth may be shorter because of the
sustained trauma, the bucco-lingual imbalance of further root growth leads to a
labial and superior displacement of the crown (our references).

At the same time, the root apex is developing against the
periosteum on the palatal side of the anterior alveolar ridge, which influences the apex to curve
further,3 in much the same way as the root apex of any other tooth
which is developing in close proximity to an anatomical limiting factor, such
as the floor of the nose, the maxillary sinus, the lower border of the mandible
and the inferior dental canal.4, 5 In these circumstances, the
further growth of the root apex becomes reoriented in a direction which is
usually parallel to the plane of that structure. Thus, undisturbed continuation
of root growth towards full apexification drives the incisal edge of the
incisor to a progressively inaccessible location, propelling it ever upwards
towards the anterior nasal spine.

If this is permitted to continue, the resulting final and
tightly curved shape of the root may not permit full corrective realignment of
the tooth while maintaining its root within the confines of the alveolar bony
ridge. Overcoming the problem at that late stage, would dictate the need for
surgical reshaping/amputation of the apex, which would secondarily necessitate elective
root canal treatment. The tooth would be left with a short root, a reduced
prognosis and the strong possibility of a deleterious change in color of the crown,
in the long term.

2 Will the situation improve
if a phase I orthodontic procedure is undertaken while the root is still
growing?

If we base ourselves on the above evidence, it is reasonable
to assume that early resolution of the impacted tooth and its alignment will
distance the developing root apex from the palatal periosteum and lead to a
more favorable shape of root end. The
vitality of the affected incisor would be maintained and much would be gained
in terms of its root length, its long term prognosis and its appearance.

3.Is it reasonable, fair or
ethical to leave a child without a central incisor for 6 years?

I believe that this statement is both the question and its
answer. For most children, the formative years of their childhood between the
ages of 6-12 years are those in which their outlook on life develops. In no
small part, a missing incisor is often the focus of derision among their own
classmates at school and elsewhere, often having a profound effect on their
personality.

Fig. 4. Occlusal and anterior views of the initial
orthodontic set-up, showing a soldered transpalatal bar and brackets bonded to
the deciduous teeth and the erupted central incisor. There is no bracket on the
right deciduous canine, which was mobile and shed naturally within a short
period thereafter. A plastic sleeve was threaded on to the archwire to prevent irritation
of the lip.

Fig. 5a. In March 2014, a full flap of attached gingiva
was raised from the crest of the ridge, to reveal the palatal side of the
inverted central incisor.

Fig. 5b. An eyelet attachment is bonded to the palatal
aspect of the incisor, as close as possible to the incisal edge. A twisted
stainless steel ligature is drawn from the eyelet and hooked over the raised
archwire, to apply extrusive force on the incisor.

Fig. 5c. The full surgical flap is sutured back to its
former place, leaving only the steel ligature visible for further activation at
succeeding visits.

The case presented here (Fig. 1-7) is of just such a child.
His phase 1 treatment was completed in 16 months, in April 2015 and at the age
of 9 years. He was provided with a maxillary removable Hawley-type of retainer,
to be worn 12 hours per day (evening and night) and advised to return for re-evaluation
12 months later.

Fig. 6a. In September 2014, the incisor had erupted
through the attached gingiva, without the need for additional reparative
surgical periodontal procedures.

Fig. 6b. In October 2014, the palatal eyelet was removed
and a bracket bonded to the labial side of the central incisor and on the newly
erupted lateral incisors.

Fig. 6c. By December 2014, the 4 incisors had been
aligned and spaces eliminated.

Fig. 7a. To achieve the considerable labial root torque
required in this and most other dilacerate incisor cases, a Begg-type auxiliary labial torqueing spring was used “piggy-back” over the main archwire. The
auxiliary is seen here in its passive state.

Fig. 7b. The torqueing force is exerted when the curved
extremities of the torqueing spring are raised to the archwire and ligated in
the brackets.

Until 10 days ago (October 2017), I had not heard from them
and I therefore initiated a direct contact. The father informed me that all was
well and that the boy had worn his retainer for about 6 months and then, 2
years ago, discarded it! They were happy with the result and were not keen to
move on to a phase 2 treatment. I pointed out to him that follow-up of the
developing permanent dentition was advised but that it was very important that
an evaluation of the status of the dilacerate incisor should be made.

In next month’s bulletin, I shall describe the new findings,
particularly in relation to the condition of the dilacerate incisor, to the interesting
pattern of continuation of its root growth and to its long term prognosis.